Tunnel Face Stability & New CPT Applications - Geo-Engineering

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140 3. Horizontal Cone Penetration TestingSand Type C 0 C 1 C 2 C 3Ticino 220 0.065 0.440 2.93Hokksund 165 0.140 0.400 3.38Table 3.7: Parameters for different sand types for use in 3.52, [87]this does not say that it is the only possible choice and it is certainly a somewhat arbitrary one,but the same could be said for other choices.In the same line of thought the vertical effective stress in VCPT theories could be replacedby the initial stress that acts in the direction of penetration in HCPT, which is the horizontaleffective stress. The idea is then to replace all instances of σh ′ in an existing VCPT theory byσ (0) and all instances of σ v ′ by σ h ′ , while keeping all other parameters unchanged. Best suitedwould of course be a theory that separately contains both stresses.A suitable candidate is the empirical relation given by Jamiolkowski [87] based on calibrationchamber tests on different sandsq V c = C 0 σ C 1v σ C 2h exp(C 3D r ) (3.52)with parameters for different sands given in table 3.7. This theory explicitly contains both initialstresses and has been derived for dry sands, so that the total stresses are equal to the effectivestresses.The relation for the horizontal sounding, derived from (3.52) according to the schemesketched above, isq H c = C 0 σ C 1h σ (0)C2 exp(C 3 D r ) (3.53)resulting in a ratio of horizontal over vertical cone resistanceq H/Vc = K C 1[ ] 1 + K C2(3.54)2KFor the parameters given in table 3.7 the resulting ratio of horizontal over vertical cone resistanceis sketched in figure 3.39 and compared with the result from (3.51). It shows the same trend ofhigher horizontal than vertical cone resistance at low K-values, only less strongly. For exampleat K = 0.5 the horizontal cone resistance is 50% greater than the vertical according to (3.51),but no more than 15% according to (3.54).The same approximation of the stress state can of course be applied to other theories. Thiswould lead to slight changes in the numerical results, but not to a fundamentally differentbehaviour, as this is mostly determined by the assumptions made in equating σh ′ in verticalpenetration with σ (0) in horizontal penetration. The conclusion already drawn in the previoussection that horizontal cone resistance is expected to be higher than vertical cone resistancewould remain unchanged.3.7 ConclusionsThe cone penetration test is highly suited for the in-situ determination of the soil characteristicsin soft soils. The interpretation of soil characteristics based on the test’s main results, the coneresistance q c and sleeve friction f s measurements, leans strongly on empirical relations. A
3.7. Conclusions 141W H/V 043Ticino SandHokksund Sand(3.51)2100 1 2KFigure 3.39: Theoretical ratio of horizontal over vertical cone resistance vs earth pressure coefficientbased on adapted VCPT modelnumber of different analytical models exists but these can only predict cone resistances for alimited range of soil types and can tackle the inverse problem of determining soil properties fromCPT measurements with varying success only.This lack of reliable analytical models for vertical CPT limits the possibilities to adapt amodel to horizontal cone penetration. The primary method to establish a correlation betweenhorizontal and vertical cone resistances is therefore to perform both tests in a soil sample underidentical conditions. The calibration chamber offers this possibility as it allows the conditioningof sand at various densities. The DUT rigid wall calibration chamber further offers the possibilityto successively execute vertical and horizontal CPTs in the same soil sample. In that way anyvariation in the soil properties due to different sample preparations is eliminated.In order to obtain a correlation between HCPT and VCPT measurements, a series of calibrationchamber tests has been executed in four differently graded sands at different densities.These tests show that measurements obtained in horizontal cone penetration tests in sand differfrom those resulting from vertical tests.Firstly, the horizontal over vertical cone resistance ratio q H/V c is larger than 1 for sands atintermediate densities, with an average value of 1.2. For low and high densities this ratio tendstowards unity. Although the scatter in the data is significant, the average of the data can bedescribed byq H/Vc = 1 + 0.191 e −13.6(D r−0.497) 2 (3.55)This behaviour of the cone resistance ratio can be understood if the assumption is made that theundisturbed lateral stress is governing the cone resistance. In vertical CPT this is the horizontalstress, whereas in horizontal CPT this stress state varies between the horizontal and verticalstress along the circumference of the cone.Given the test setup of the calibration chamber and the preparation of the sand by fluidisationand vibration, a relation is established between density and horizontal stress, in that higherdensities are accompanied by higher horizontal stresses. For higher densities the coefficientof effective horizontal stress tends towards unity, so that no difference between horizontal andvertical stress exists and as a result no difference in the stress state perpendicular to the penetrationdirection. This explains the fact that the measured cone resistance ratio tends towards one forhigh densities.For loose packed sands the stress state is known to have little influence on the cone resistance,as has been established for example in calibration chamber tests by Jamiolkowski. As a result it
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Tunnel Face Stability&New CPT Appli
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Dit proefschrift is goedgekeurd doo
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viAcknowledgementsKolla här, min
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viiiAbstractThe tunnel wound on and
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xContents3.2.4 Finite Element Model
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xiiList of Symbols× ij i = j norma
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xivList of Symbolsλfirst Lamé con
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1.2. Outline of this Thesis 3suppor
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Chapter 2Stability Analysis of the
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2.1. Introduction 7fluidsoilzs Fα
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2.1. Introduction 9Figure 2.3: Unsu
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2.1. Introduction 11q sq sq sααα
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φ = 40 ◦φ = 35 ◦2.1. Introduc
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2.1. Introduction 15T 1 T 1E1 E 1G
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2.1. Introduction 17N Deformation<
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2.1. Introduction 19GC45 ◦ + φ/2
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2.1. Introduction 21Figure 2.19: Ce
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2.1. Introduction 23Figure 2.21: In
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2.1. Introduction 25D (m) Soil type
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2.2. Wedge Stability Model 27the su
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2.2. Wedge Stability Model 29xyhz =
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2.2. Wedge Stability Model 31s ′
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2.2. Wedge Stability Model 33q 02ad
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2.2. Wedge Stability Model 35200400
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2.2. Wedge Stability Model 37with a
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2.2. Wedge Stability Model 39s(z t
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2.2. Wedge Stability Model 41∆p f
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2.2. Wedge Stability Model 43has be
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2.2. Wedge Stability Model 45from t
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2.2. Wedge Stability Model 47γF(t/
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2.2. Wedge Stability Model 49s min
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2.2. Wedge Stability Model 5140∆s
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2.3. Model Sensitivity Analysis 53P
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2.3. Model Sensitivity Analysis 55i
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2.3. Model Sensitivity Analysis 57
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2.3. Model Sensitivity Analysis 63t
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2.3. Model Sensitivity Analysis 65o
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2.4. Comparison with Field Cases 67
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Figure 2.57: Overview of soil strat
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Page 103 and 104: 2.4. Comparison with Field Cases 89
Page 109 and 110: 2.5. Further Groundwater Influences
Page 111 and 112: 2.6. Conclusions 97the effective st
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Page 115 and 116: Chapter 3Horizontal Cone Penetratio
Page 117 and 118: 3.2. Interpretation of Cone Penetra
Page 123 and 124: 3.3. Calibration Chamber Tests on S
Page 143 and 144: 3.4. Scale Model Tests 129Figure 3.
Page 145 and 146: 3.4. Scale Model Tests 1315210Figur
Page 147 and 148: 3.5. Field Tests 133Figure 3.35: Pl
Page 149 and 150: 3.6. Modelling Horizontal Cone Pene
Page 151 and 152: 3.6. Modelling Horizontal Cone Pene
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Page 157 and 158: Chapter 4High-Speed Piezocone Tests
Page 159 and 160: 4.2. Determination of Liquefaction
Page 161 and 162: 4.2. Determination of Liquefaction
Page 163 and 164: 4.4. Calibration Chamber Tests 149
Page 165 and 166: 4.4. Calibration Chamber Tests 1518
Page 167 and 168: 4.4. Calibration Chamber Tests 153v
Page 169 and 170: 4.4. Calibration Chamber Tests 155-
Page 171 and 172: 4.5. Conclusions and Recommendation
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Page 175 and 176: Chapter 5Conclusions and Recommenda
Page 177 and 178: 5. Conclusions and Recommendations
Page 179 and 180: Bibliography[1] M.Y. Abu-Farsakh, G
Page 181 and 182: Bibliography 167[30] B. Belter, W.
Page 183 and 184: Bibliography 169[65] J.K. van Deen.
Page 185 and 186: Bibliography 171[99] E. Kreyszig. A
Page 187 and 188: Bibliography 173[133] Committee on
Page 189 and 190: Bibliography 175[171] F.W.J. van Vl
Page 191 and 192: Curriculum VitaeWout Broere was bor
Page 193 and 194: SamenvattingGraaffrontstabiliteit &
Page 195 and 196: Samenvatting 181spanningen ook in d
Page 197 and 198: NawoordIn de afgelopen jaren heb ik
Page 199 and 200: Appendix ABasic Equations of Ground
Page 201 and 202: A.1. Semi-confined System of Aquife
Page 203 and 204: A.2. Transient Flow 189withS s the
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....Appendix BBasic Equations of El
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B. Basic Equations of Elasticity 19
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